The Extent of Fusion Within the Congenital Klippel-Feil Segment

Retrospective radiographic review. To evaluate in patients with Klippel-Feil syndrome (KFS) the presence and extent of specific fusion patterns across involved cervical segments and their association with age-specific parameters. While the radiographic hallmark of KFS is characterized by congenital fusion of at least one cervical motion segment, the relation between age and the extent of segmental congenital fusion remains speculative. A radiographic review of 31 patients with KFS at a single institution. Plain radiographs were used to assess fusion across the vertebral segment as entailing the anterior elements, posterior elements, or complete segment from O-T1. Age-specific stratifications were also performed. A mean of 3.7 fused segments and a sum of 116 fused segments were noted. From C2-T1, complete fusion of the involved segment represented 77.8% at 10 years or older, 87.5% at 15 years or older, 91.7% at 16 years or older, 95.7% at 17 years or older, 86.5% who were skeletally mature, and 100% at adulthood. Similar trends were not noted for segments of O-C2. In absence of complete segmental fusion, the posterior elements exhibited a higher incidence of fusion than the anterior elements. Statistically significant differences between anterior/posterior to complete segmental fusion with respect to different age markers entailed segments of C2-C3, C4-C5, and C6-C7 (P < 0.05). This study provides some insight into the potential developmental aspects of the extent of segmental fusion of the cervical spine in patients with KFS. In older patients, complete fusion of involved fused segments was more prevalent in regards to C2-T1; however, such an observation was not noted for segments from O-C2. In the absence of complete segmental fusion, fusion of the posterior elements was more often noted than fusion of the anterior elements. Awareness of the varied phenotypic expression of segmental fusion patterns of the cervical spine in patients with KFS underlines theimportance of thorough evaluation of the cervical spine to assess the presence and extent of segmental fusion to facilitate in the identification of neurologic risk factors.